Matplotlib different size subplots

I need to add two subplots to a figure. One subplot needs to be about three times as wide as the second (same height). I accomplished this using GridSpec and the colspan argument but I would like to do this using figure so I can save to PDF. I can adjust the first figure using the figsize argument in the constructor, but how do I change the size of the second plot?

• As of matplotlib 3.6.0, width_ratios and height_ratios can now be passed directly as keyword arguments to plt.subplots and subplot_mosaic, as per What's new in Matplotlib 3.6.0 (Sep 15, 2022).

f, (a0, a1) = plt.subplots(1, 2, width_ratios=[3, 1])

f, (a0, a1, a2) = plt.subplots(3, 1, height_ratios=[1, 1, 3])

• Another way is to use the subplots function and pass the width ratio with gridspec_kw
  • matplotlib Tutorial: Customizing Figure Layouts Using GridSpec and Other Functions
  • matplotlib.gridspec.GridSpec has available gridspect_kw options

import numpy as np
import matplotlib.pyplot as plt 

# generate some data
x = np.arange(0, 10, 0.2)
y = np.sin(x)

# plot it
f, (a0, a1) = plt.subplots(1, 2, gridspec_kw={'width_ratios': [3, 1]})
a0.plot(x, y)
a1.plot(y, x)

f.tight_layout()
f.savefig('grid_figure.pdf')

• Because the question is canonical, here is an example with vertical subplots.

# plot it
f, (a0, a1, a2) = plt.subplots(3, 1, gridspec_kw={'height_ratios': [1, 1, 3]})

a0.plot(x, y)
a1.plot(x, y)
a2.plot(x, y)

f.tight_layout()